support preview versions

DotNetSolutionTools.Core/DotNetUpgrade.cs

@@ -2,6 +2,7 @@
 using Microsoft.Build.Construction;
 using Microsoft.Build.Definition;
 using Microsoft.Build.Evaluation;
+using NuGet.Versioning;
 
 namespace DotNetSolutionTools.Core;
 
@@ -24,54 +25,71 @@ public static class DotNetUpgrade
                 .PropertyGroups
                 .SelectMany(x => x.Properties)
                 .FirstOrDefault(x => x.Name == "TargetFramework");
-            if (targetFramework?.Value is "net7.0" or "net6.0" or "net5.0")
+            if (targetFramework?.Value is "net8.0" or "net7.0" or "net6.0" or "net5.0")
+            {
+                if (targetFramework.Value is not "net8.0")
                 {
                     targetFramework.Value = "net8.0";
                     project.Save();
                     FormatCsproj.FormatCsprojFile(project.FullPath);
                 }
-
                 await UpdatePackagesToLatest(project);
             }
         }
+    }
 
     public static async Task UpdatePackagesToLatest(ProjectRootElement project)
     {
-        var evalProject = Project.FromProjectRootElement(
+        Project? evalProject = null;
+        try
+        {
+            evalProject = Project.FromProjectRootElement(
                 project,
                 new ProjectOptions() { LoadSettings = ProjectLoadSettings.IgnoreMissingImports }
             );
-        var packages = evalProject.Items.Where(x => x.ItemType == "PackageReference");
+            var packages = evalProject.Items.Where(x =>
+                x.ItemType == "PackageReference" && x.HasMetadata("Version") &&
+                x.EvaluatedInclude.StartsWith("Microsoft.")).ToList();
+            
             var packageNameAndVersion = packages
-            .Where(s => s.EvaluatedInclude.StartsWith("Microsoft."))
                 .Select(
                     x =>
                         new
                         {
                             Package = x,
                             Name = x.EvaluatedInclude,
-                        Version = Version.Parse(
+                            NugetVersion = NuGetVersion.Parse(
                                 x.Metadata.First(s => s.Name == "Version").UnevaluatedValue
                             )
                         }
                 )
                 .ToList();
 
-        var shouldFormat = false;
+            var shouldSave = false;
             foreach (var package in packageNameAndVersion)
             {
                 var latestNugetVersion = await NugetLookup.FetchPackageMetadataAsync(package.Name);
-            // it will compare 6.8.0.0 to 6.8.0, and says left is newer, we dont want to say its newer, so use the normalized string to make a new version
+                
-            var normalizedVersion = Version.Parse(latestNugetVersion.ToString());
+                if (latestNugetVersion > package.NugetVersion)
-            if (normalizedVersion > package.Version)
                 {
-                shouldFormat = true;
+                    shouldSave = true;
                     package.Package.SetMetadataValue("Version", latestNugetVersion.ToString());
                 }
             }
 
+            if (shouldSave)
+            {
                 project.Save();
-        if (shouldFormat)
                 FormatCsproj.FormatCsprojFile(project.FullPath);
             }
         }
+        finally
+        {
+            if (evalProject is not null)
+            {
+                ProjectCollection.GlobalProjectCollection.UnloadProject(evalProject);
+                ProjectCollection.GlobalProjectCollection.TryUnloadProject(project);
+            }
+        }
+    }
+}